The present invention relates in general to power rams or pile drivers and in particular to an impact transfer unit made of steel and arranged between a hammer and a driven member to transfer impacts from the hammer body.
In prior-art ramming devices it has been known how to employ a percussion plate, a driving cap or the like between the drop hammer and the driven part in order to prevent deformation or damage of the latter. Such percussion plates or driving caps are provided usually with one or more inserts of a suitable buffer material capable of withstanding the extremely hard blows of the hammer. Such buffer means have included blocks or plates of hard wood, plastic, asbestos or aluminum, on the one hand, or layers of steel cables or cup springs, on the other hand. Due to the fact that such buffer materials, during the operation of the ram, are exposed to excessively large striking forces and sooner or later are destroyed and must be exchanged, there result inconvenient interruptions of the working process, timeconsuming auxiliary work and additional operational expenses. For this reason, impact transfer devices have been devised including a prestressed pressurized gas cushion enclosed in a cylinder under a movable striking piston. Such known impact transfer devices, however, due to the necessarily high prestressing forces and the resulting sealing problems, are complicated and expensive.